The 2020 Creek Fire was a very large wildfire in central California's Sierra National Forest, in Fresno and Madera counties. One of the most significant fires of California's record-setting 2020 wildfire season, it began on September 4, 2020, and burned 379,895 acres (153,738 ha) over several months until it was declared 100% contained on December 24, 2020. The Creek Fire is the fifth-largest wildfire in recorded California history and the second-largest single fire—i.e. not part of a larger wildfire complex—following the 2021 Dixie Fire.

Tens of thousands of residents in Fresno and Madera counties were forced to evacuate, and the fire also necessitated the helicopter rescue of hundreds of people by the California National Guard after they became trapped at Mammoth Pool Reservoir. Despite this, the fire caused zero fatalities, though there were more than twenty injuries. The Creek Fire destroyed hundreds of structures in Sierra Nevada communities, adding up to 856 buildings destroyed and dozens more damaged. The combined cost of the months-long firefighting effort and damage to private and county property exceeded $500 million.

Background

The Creek Fire occurred amid an already quite active wildfire season in California, which until early September had largely been driven by an outbreak of dry thunderstorms in mid-August. Between August 15 and September 9 alone, more than 1.6 million acres (650,000 ha) had burned, more than five times California's average acreage burned by that date. Over Labor Day weekend, the state suffered "one of its hottest weekends in memory", leading the National Weather Service to issue widespread heat advisories and red flag warnings. The first two days of the Creek Fire's growth saw abnormally hot and dry conditions for the region.

The Creek Fire burned largely in the Sierra National Forest, which spans more than 1.3 million acres (530,000 ha) at an elevation range of ~900–14,000 feet (270–4,270 m). The burn area largely comprised mixed coniferous forest containing ponderosa pine, sugar pine, white fir, incense-cedar, and California black oak trees. Bark beetle infestation and California's drought between 2012 and 2016 killed almost 150 million trees in the Sierra Nevada, including more than 36 million trees in the Sierra National Forest alone between 2015 and 2019—the most of any national forest in California. Tree mortality rates reached 80% in what became the Creek Fire footprint. The U.S. Forest Service estimated that dead stands of trees that burned in the fire contained 2,000 tons of fuel for every one acre (0.40 ha).

Progression

September 4–5

According to the U.S. Forest Service, the Creek Fire began at approximately 6:45 p.m. PDT on Friday, September 4, 2020, in the Big Creek drainage area between Shaver Lake, Big Creek, and Huntington Lake, California. The fire had burned 2,000 acres (810 ha) by the following morning and 5,000 acres (2,000 ha) by that afternoon.

Driven by powerful diurnal up-canyon winds within the San Joaquin River drainage, the Creek Fire quickly became a firestorm. Roughly eighteen hours after the fire had begun, the Creek Fire began producing a pyrocumulonimbus cloud, which, observed by radar and satellite, became one of the largest such events on record in the United States, or even North America. The fire was fed in part by these cloud formations, which generated downdrafts that supplied the fire with additional oxygen and pushed it across fire lines. The fire has been characterized as a plume-dominated blaze, where the environment allows for the continued upward blowing of smoke and the vertical transfer of heat, causing extreme fire behavior, such as multiple fire tornadoes observed using Doppler weather radar data.

The Creek Fire also spawned two fire tornadoes on September 5; the first was rated EF2 near Huntington Lake with approximately 125 mph winds, and the second was rated EF1 near Mammoth Pool with approximately 100 mph winds. Damage included uprooted pine trees as well as stripped bark. These "firenadoes" formed due to the intense heat the fire had generated, which pulled in air, creating rotational vortices. The Mammoth Pool firenado trapped hundreds of campers in the area, while the Huntington Lake one caused severe damage to trees in the Camp Silver Fir, B.S.A. & Kennolyn Camps area, and continued to attack their root systems a week later, burning underground at over 1,500 °F (820 °C).

The fire had initially trapped about 1,000 people near Mammoth Pool Reservoir after it jumped the San Joaquin River, with at least 200 individuals trapped at a boat launch. The California National Guard, using CH-47 Chinook and UH-60 Black Hawk helicopters and night goggles, flew multiple sorties to evacuate people from near Mammoth Pool Reservoir. The Chinook flew three flights, carrying 67, 102, and 37 people each time (not including crew). The Black Hawk flew another three times, carrying 15, 22, and 21 people each time. Evacuees were taken to an airfield in Fresno.

September 6–9

Within the first four days, the Creek Fire rapidly exploded, expanding anywhere between 20,000 acres (81 km) to 50,000 acres (200 km) each day from September 4–9. Reasons for this explosive behavior included strong, gusty winds pushing east from the Central Valley into the Sierra Nevada and a pileup of dead trees due to the 2011–17 California drought and subsequent bark beetle infestation.

September 10 onwards

Thick smoke lying over the fire, as well as reduced winds and lower temperatures, allowed firefighters to notch six percent containment by September 10.

With over 290,000 acres (1,200 km) burned on September 23, the Creek Fire became the largest single blaze (i.e. not a wildfire complex) in the history of California, though it was surpassed just one year later by the 2021 Dixie Fire in Northern California.

Over the next month, the Creek Fire continued to grow in size, exceeding 300,000 acres (120,000 ha) on September 27. In October, most of the new growth in the Creek Fire was coming from the eastern flank of the fire, which was expanding towards Mono Hot Springs and Lake Thomas A Edison. On October 26, the Creek Fire had grown to 369,362 acres (149,475 ha), while containment was at 63 percent.

The fire was fully contained on December 24.

Cause

The U.S. Forest Service Law Enforcement and Investigations department led the investigation into the cause of the Creek Fire, with assistance from the California Department of Forestry and Fire Protection (Cal Fire). On July 16, 2021, the U.S. Forest Service announced that the results of its months-long investigation into the cause of the Creek Fire had been inconclusive. According to Dean Gould, the supervisor of the Sierra National Forest, investigators "spent countless hours hiking rugged terrain to determine the cause, interviewed numerous leads, and eliminated multiple potential causes." The Forest Service ruled out that the fire had been sparked by equipment use, an escaped campfire, powerlines, or spontaneous combustion, among multiple other discarded possibilities. Investigators judged that the "most probable cause" of the fire was a lightning strike, but noted that they could not rule out arson or smoking. The lightning strike assessment was substantiated by a Douglas fir snag, bearing signs of lightning damage, that early-arriving firefighters had seen going up in flames. The Creek Fire's cause is officially listed as "undetermined".

Effects